Disk drive devices using various kinds of recording disks, such as optical disks, magneto-optical disks, flexible magnetic disks, and the like, have been known in the art. In particular, hard disk drives (HDDs) have been widely used as storage devices of computers and have been one of indispensable storage devices for current computer systems. Moreover, the HDDs have found widespread application to moving image recording/reproducing apparatuses, car navigation systems, cellular phones, and the like in addition to the computers, due to their outstanding characteristics.
A magnetic disk used in a HDD has multiple concentric data tracks and servo tracks. Each data track includes a plurality of data sectors containing user data recorded thereon. Each servo track has address information. The servo track consists of a plurality of servo data arranged discretely in the circumferential direction, and one or more data sectors are recorded between servo data. A head element portion accesses a desired data sector in accordance with address information in the servo data to write data to and retrieve data from the data sector.
The head element portion is formed on a slider; the slider is bonded to a suspension of an actuator. The assembly of the actuator and the head slider is called a head stack assembly (HSA) and the assembly of the suspension and the head slider is called a head gimbal assembly (HGA). Pressure caused by air viscosity between an air bearing surface (ABS) of the slider facing a magnetic disk and the spinning magnetic disk balances pressure toward the magnetic disk added by the suspension so that the head slider flies over the magnetic disk with a specific gap. The actuator pivots about a pivotal shaft to move the head slider to a target track and position it onto the track.
As a track per inch (TPI) in the magnetic disk increases, improvement in positioning accuracy of head slider has been required. However, driving the actuator with a voice coil motor (VCM) has found a limit in the positioning accuracy. Therefore, an approach has been proposed that mounts a compact actuator (microactuator) on a tip end of the actuator to achieve a finer positioning (for example, refer to U.S. Patent Application Publication No. 2006/044698).
A magnetic disk is charged by external electromagnetic waves or noise generated by a spindle motor. Since the magnetic disk and a head slider have capacitance therebetween, electric charge is induced to the head slider at a high frequency. In order to avoid a head element portion from being damaged by electrostatic discharge (ESD) from the head slider, it is necessary that the slider body of the head slider be grounded. If the head slider is bonded to a microactuator, it is necessary that the head slider be grounded through the microactuator (for example, refer to Japanese Unexamined Patent Application Publication No. 2004-247027).